Bogs, marshes, swamps, fens, and peatlands are all various types of wetland habitat. Wetlands can be either seasonal or permanent, and are characterized by soil that is persistently inundated with water. Vegetation can vary widely, including everything from trees to simple grasses and reeds.

Due to the constant presence of large amounts of water, many wetlands have an active ecosystem under the water. It's impossible to describe the range of fish and crustaceans that live in wetlands, but some examples are crabs, catfish, lungfish, and mussels. These creatures also provide an abundant food source for many types of riverine birds. Herons, stilts, and bitterns are common sights in many wetlands throughout the world.

Reptiles and amphibians tend to be well represented in wetland ecosystems. Amphibians require water nearby in order to thrive, and wetlands provide the perfect habitat that mixes aquatic and terrestrial environments. This is why many swamps and marshes have such large frog and salamander populations. Additionally, many reptiles have become well adapted to the water. Some, like the alligator, have even become the apex predators of their ecosystem.

Most wetlands have relatively high insect populations. The easy breeding conditions provided by the standing water provides many species with an easy habitat to survive in. Mayflies, dragonflies, and mosquitos all find plentiful food and numerous breeding grounds in wetlands.